Various protection mechanisms for lithium ion batteries exist. If a lithium ion battery overcharges, strong exothermic reactions are possible and the potential for causing a fire increases. To prevent a lithium ion battery from overcharging, a battery protection circuit is used. The battery protection circuit often contains, among other components, two FET (field effect transistor) switches and a control integrated circuit. One FET prevents current from flowing into the battery, while the other prevents current from flowing from the battery unless the control IC enables it.
Battery protection circuits often protect cell phones, smart phones, and computer tablets. In such electronic devices, space for components on a circuit board must be kept to a minimum. Accordingly, not only are the device components themselves kept to a minimum size, but the packaged device(s) must also be kept to a minimum. A typical battery management circuit 10 is shown in FIG. 1. A system 11, such as a cell phone, personal computer, etc., has a battery 18 for operating the system 11. A power management circuit 12 regulates the operation of two power mosfets 2, 4 which will charge and discharge the battery 18. A secondary protection circuit 14 is disposed between a fuse 16 and lines connecting the battery 18 to the power management circuit 12. The power management circuit prevents the battery from overcharging and from excessive discharging which would prevent future recharging of the battery.
The individual mosfets 2, 4 have been separately packaged and wired together as shown in FIG. 1. However, as systems are made smaller, there is a need for reducing the net area occupied by the mosfets and a corresponding requirement that devices operating in the reduced areas perform as well or better than devices with larger areas. These requirements present challenges to those skilled in the art because reducing the size of a mosfet generally increases the resistance of the series connected mosfets, or RSS (resistance source-to-source).
Embodiments of the invention are not limited to such uses as structures as shown herein and other uses and embodiments of the invention may be contemplated. For example, exemplary embodiments may be mounted to circuit boards along with other components in electrical systems such as computer systems, servers, wireless phones, televisions, power supplies, etc. Embodiments of the invention are robust and stable. Aspects of the semiconductor die package provide greater packaging efficiencies than previously encountered, as well as excellent thermal performance due to the exposed IC die attach pad and clip structures. This allows for smaller space requirements, cost savings and easier manufacturing procedures for applications such as LCD electronics. Furthermore, in exemplary embodiments, the placement of a half bridge circuit on each of opposite surfaces of the leadframe creates more stable and rigid circuitry. In such placement, the clip structures can be exposed by the molding material on both the back and front sides of the package, allowing for good thermal performance.
As used herein “top” and “bottom” surfaces are used in the context of relativity with respect to a circuit board upon which the semiconductor die packages according to embodiments of the invention are mounted. Such positional terms may or may not refer to absolute positions of such packages.
The semiconductor die packages described above can be used in electrical assemblies including circuit boards with the packages mounted thereon. They may also be used in systems such as phones, computers, etc.
Any recitation of “a”, “an”, and “the” is intended to mean one or more unless specifically indicated to the contrary. The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described, it being recognized that various modifications are possible within the scope of the invention claimed.
Moreover, one or more features of one or more embodiments of the invention may be combined with one or more features of other embodiments of the invention without departing from the scope of the invention.